Footwear insoles are generally inserted into shoes, in order to provide added cushioning or support for the wearer of the shoes. The insoles may be removable and reusable, and they may be one-size-fits-all, specified shoe sizes, or custom-sized to the wearer.
Some insoles offer additional cushioning by providing one or more cushioning layers to the soles of the wearer's shoes. These insoles are generally used to decrease the impact felt by the wearer during walking, jogging, running, or other activities.
For example, U.S. Pat. Nos. 5,068,983 and 5,146,698 describe a combination of foam materials for a resilient base piece, a heel piece, and a top cushioning layer to absorb shock and impact.
Other insoles offer additional foot support by providing a rigid, formed layer placed on top of the soles of the wearer's shoes. These insoles are generally provided to correct abnormal conditions of a wearer's feet or gait.
For example, U.S. Pat. Nos. 6,125,557; 6,269,555; 6,601,320; and 7,124,518 describe a two-piece orthotic assembly having a post member and a plate member for positioning and controlling motions of a wearer's foot in a shoe. U.S. Pat. No. 4,317,293 describes an insole of resiliently elastic material and a stiffening insert at the outside of the foot to ensure a natural position when standing and a natural rolling motion when walking. U.S. Pat. No. 6,502,330 describes a sole strengthener for stabilizing lateral movement of the foot and guiding longitudinal movement of the foot. U.S. Pat. No. 6,732,456 describes an orthotic having a built-in step indicating device (ball) to correct excessive pronation and supination of the foot. U.S. Pat. No. 6,745,501 describes an orthotic having a rigid cap member to correct an abnormal toe-off phase of a gait cycle and prevent shuffling of the toe-off phase by tilting the foot forward via a transverse ridge portion on the underside of the rigid cap member.
Still other insoles provide additional support to specific areas of the foot. For example, U.S. Patent Application No. 2008/0072461 describes an orthotic having a cushioning layer and an outer shell layer, which may optionally include an inner shell insert layer for arch support. In addition, U.S. Patent Application No. 2007/0289170 describes an orthotic having a cushioning layer and a shell layer with a removable insert for arch support. U.S. Pat. Nos. 6,233,847 and 6,618,960 describe a thin, rigid, resiliently flexible cap under a soft, cushioning foam blank to provide proper support to heel and rearfoot areas. U.S. Patent Application Nos. 2002/0050080; 2003/0009915; 2007/0277400; and 2008/0010861 generally describe orthotics for providing support to various areas of the foot.
Some insoles have been proposed to relieve pain in the wearer's knees from medial knee osteoarthritis, with varying results. In this regard, several studies have been conducted to try to confirm the alleviation of knee osteoarthritis by the use of laterally-wedged foot orthotics. For example, in a study by D. Casey Kerrigan et al. described in Effectiveness of a Lateral-Wedge Insole on Knee Varus Torque in Patients with Knee Osteoarthritis, ARCH PHYS MED REHABIL, Vol. 83, pp. 889-893 (July 2002), knee varus torque in medial knee osteoarthritis was reduced by using rubber-like foam, lateral-wedge insoles. However, in another study by Kristin Baker et al. described in A Randomized Crossover Trial of a Wedged Insole for Treatment of Knee Osteoarthritis, ARTHRITIS & RHEUMATISM, Vol. 56, No. 4, pp. 1198-1203 (April 2007), no statistically significant or clinically important pain relief in medial knee osteoarthritis was found by using incompressible, laterally-wedged foot orthotics.
Further, specifically for alleviating foot arthritis pain, U.S. Pat. Nos. 7,284,342; 6,481,120; and 5,611,153 describe insoles for alleviating foot arthritic problems by using insoles with cushioning layers and pressure redistribution layers. In addition, the American Academy of Orthopaedic Surgeons suggests a soft arch support with a rigid heel for alleviating foot arthritis pain (http://orthoinfo.aaos.org/topic.cfm?topic=A00163).